The present invention provides a blast joint and method of making the same. The joint produced is designed to be suitable for use in oil and/or gas wells producing to flow of fluid comprising gas, at high pressure, with resultant flow of fluid and entrained solid particles at high velocity escaping. The flow of gas at high velocity from an underground high pressure source, with or without accompanying oil or other liquid, entrains solids, particularly grains of sand. The escaping blast has a highly abrasive or cutting effect upon the surfaces of solids-- particularly metals--with which such flow comes into contact.
Blast tubes constructed of cemented tungsten carbide or like abrasion resistant material, have previously been proposed but never, so far as is known to applicant, brought into successful practice, first, because it is a most refractory material, difficult to work, heavy, brittle, hard to produce, difficult to apply, and of exceeding hardness. The properties of cemented tungsten carbide and equivalent materials are well known.
The second factor which would tend to limit its use is the cost of the material and its fabrication. Also to be considered is the question of whether it will pay for itself.
It is chiefly the greater number of deep wells wherein gas at exceptionally high pressure is encountered that has caused the oil producers to call for equipment that can stand up to the extremely severe condition of sand, driven in a high velocity stream of gas and/or liquid.
The difficulty and expense of pulling a string of tubing on a deep off-shore well is so great that it offers an inducement to the production of a blast joint that is practically indestructable even though the cost of the joint be high.
The impact effect of solid particles moving in a stream of gas is a function of MV.sup.2 where M is the mass of the particle and V is the velocity thereof. Velocity is the unpredictable factor.
Consequently, the problem of maintaining the integrity of the well equipment, particularly the production tubing used at depths and pressures--such as were encountered in connection with Shell Oil Company Well designated as "No. 1 Ridgeway Management 35-3-N-2E"--is extremely difficult. The Oil and Gas Journal of June 2, 1975 reports that although it was a producing well, it was abandoned
"Bottom hole pressure of 22,000 psi was encountered, believed to be the highest for a producing well anywhere in the world." [OGJ, Jan. 6, page 20]
The length of the completed blast joint and the method of producing the joint of the present invention are preferably, but not necessarily, dependent on standard lengths, sizes and joints of tubing generally employed throughout the industry. As a practical matter, the length of the blast joint of this invention is, preferably but not necessarily, substantially equal to the standard length of production tubing in order to fit in with the handling and storage facilities available at a well head, and particularly at an offshore platform. The chief variable factors are the location of the level or levels at which entry of the well fluid is admitted to the flow tube, the pressures of the fluid encountered, and the nature of the solids entrained in the outflow.